SOME EFFECTS OF VALVE FRICTION AND STICK FRICTION ON CONTROL QUALITY IN A HELICOPTER WITH HYDRUALIC-POWER CONTROL SYSTEMS

摘要

Tests have been made of a hydraulic-power-controlled helicopter to determine the effect of friction in the servovalves and the effect of stick friction when the valve friction is present.nThe tests showed that, when the valve friction is equivalent to about 7/4 pounds of force at the stick, precision flying is difficult and more work is required of the pilot. Control quality is improved by adding an amount of stick friction that is equal to the valve friction. The total of the two frictions, however, should not exceed 3 pounds. The lowest valve-friction value tested was — pound, and the pilots con?sidered the effect to be negligible and therefore considered any stick friction to be unnecessary. The pilots believed that the system was markedly improved when the valve friction was reduced from 7/4 pounds to 1/4 pound. The addition of feel devices resulted in an overall improve?ment in the control systems and was, therefore, considered to be very-desirable.